Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so forth. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems including E-UTRA, and orthogonal frequency division multiple access (OFDMA) systems.
High-speed downlink packet access (HSDPA) is a protocol for high-speed data transfer in mobile cellular networks based on the W-CDMA standard, or 3GPP. In a version of HSDPA known as dual cell HSDPA (DC-HSDPA), data from a Node B to a UE may be transmitted on the downlink using up to two carriers. On the UE side, the UE may signal the acknowledgment status of the downlink carriers by transmitting ACK, NACK, or DTX on an uplink channel, e.g., an HS-DPCCH channel.
In prior implementations of multi-carrier HSDPA, a signaling mechanism is provided in which the acknowledgment status for up to two carriers is mapped onto a specific codeword according to a codebook, and the symbols of the codeword are spread onto the HS-DPCCH channel using a spreading factor of 256. In a newer version of HSDPA known as four carrier HSDPA (4C-HSDPA), wherein up to four carriers may be transmitted to the UE on the downlink, alternative signaling mechanisms on the uplink are needed to signal the acknowledgment status for the greater number of downlink carriers.
It would be desirable to provide an acknowledgment status signaling scheme for 4C-HSDPA which advantageously utilizes existing techniques, e.g., pre-existing HSDPA channel formats and codebooks, to the greatest extent possible. It would be further desirable to introduce new techniques, e.g., new channel formats and new codewords, as necessary to accommodate the additional scenarios that specifically arise in 4C-HSDPA.